The Weight Game

[GrinP]

Time and again, someone will write a post describing how they shaved 8 oz. off their bike and a bunch of folks will shit all over them and tell them to save their effort and just say "no" to that second hamburger/beer/donut/etc.  Not only is this mean-spirited, I think it ignores a big chunk of the physics of the thing.

Okay, I get it.  For acceleration (and braking), it matters not whether the 2 lbs. is in your gut or your bike's rear shock (actually, as far as center of gravity goes, it would probably be better if the 2 lbs. was in the shock).

But I believe that is an overly simplistic view of the physics.  For most other aspects of this delicate and sublime dance we call motorcycle riding I think it does matter.  I think there is a fundamental difference between bike weight and rider weight.

Here's how I see it.  The act of riding a motorcycle is our, sometimes futile, attempt to control its trajectory using our brain and body.  Broadly, we do this in two ways.  Control inputs (i.e. moving the handlebars, twisting the throttle, etc.) and weight shifting (weighting and de-weighting the pegs, pulling up on the bars, shifting our weight forward or back or side-to-side).  It is in this weight-shifting aspect that the difference lies.  Basically, we are attempting to use our mass to influence the mass of the motorcycle.  The ratio of the riders mass to the motorcycle's mass determines how much effort will be required to influence its trajectory. In this case, you are much better off if the 2 lbs. is in your gut rather than the shock; you stand a much better chance of influencing the bike's trajectory.

Case in point.  I weigh about 170 lbs. with gear.  For two years I rode a DRZ400S (about 300 lbs.).  That bike out-weighed me almost 2:1 (57%).  I had to throw myself around like an enraged (albeit tiny) Silverback to influence it's trajectory.  Sometimes I was just a passenger.  If I weighed 200 lbs. I'd have had more influence.  Now I'm riding a CRF230 (about 250 lbs.).  The ratio of rider weight to bike weight is 68%.  Now I know lots of other things are in play here (seat height, wheelbase, engine characteristics, etc.) but it is much easier for me to influence the trajectory of the CRF.  My mass has a bigger influence.

I'm not a weight fascist.  I don't excessively drill things and I WILL have that second beer. But I don't bemoan those who do (or don't).  And if I can shave 2 lbs. off my bike I'm thrilled because I know it will pay dividends in many aspects of riding.  Personal weight loss is an admirable thing; and if you are overweight then you will feel much better and your riding will improve if you shed some pounds.  Bike weight loss is also an admirable thing.  Every ounce shed will improve your bike's handling.  And tinkering with your bike on those long winter nights is certainly better than a lot of the other things we could be doing.
 

[mixxer]

VERY well written...!

 

 

[VortecCPI]

Talk about mass...  Spend some time on top of huge bikes like XL600 or XR600...

How Scott Summers does what he does with BRP XR600 is truly remarkable...

100% agreed heavy CRF230 feels and handles like it is much lighter...

Edited March 13, 2019 by VortecCPI

[bajatrailrider]

Saving pounds is always good to a point. On trail bikes we add so much weight I don't think we care. As Im thinking the same guys that worry about weight on trail bike. Are the same ones that do not carry anything to fix a flat or other problems. A few that we ride with Jack and Pollo ride 250 and 450YZs. They love there light bikes but every other ride flat tire or anything. They ruin the whole ride for us I know we don't ride in a motorcycle park or \\\area just for motos to ride. I also know sure if you race the bike any extra  weight not good. So bottom line I would be happy to shed 20 pounds because of the 50 pounds I added. HAAAAA So how many weight saver junkies that don't race ride 100 miles at a time. Carry anything but beer in the backpack. I just pulled my small saddle bags off to clean the mud off my bike. Seems like I need reduce spare parts in saddle bags. I know some will chime in say I never carry a plug or wrench. Because I never foul a plug. It only happed to me 3 times in 50 years. One 2 stroke  Two 4 smokes. Where it happened the bikes would still be there.

[mixxer]

Another topic of weight is rotational mass....

Heavy wheels and tires, chains , sprockets being the core if this for me....

Not only do those parts have to be accelerated with the bike... They have to be accelerated in their own vectors/ rotations...

So they count for a lot more power absorption....

Pick a lighter rear tire ... You will think you just added compression when you next twist the throttle....

[RedMesa]

18 hours ago, GrinP said:

Time and again, someone will write a post describing how they shaved 8 oz. off their bike and a bunch of folks will shit all over them and tell them to save their effort and just say "no" to that second hamburger/beer/donut/etc.

Good stuff, thank you. I headlined the link in the "Weight reduction" section: http://bit.ly/2Ox578u

[RedMesa]

11 hours ago, bajatrailrider said:

I know some will chime in say I never carry a plug or wrench. Because I never foul a plug. It only happed to me 3 times in 50 years. One 2 stroke  Two 4 smokes. Where it happened the bikes would still be there.

You raise an important point. I go back and forth. Not currently carrying wrench and plug on CRF230F. Could be a big mistake and these items are not real large.

It does have an Iridium plug in it; bought that before I learned they are more for high compression engines.  Especially those run slower. For example, the Beta Xtrainer comes with Iridium while the race Betas don't, IIRC.

So, 50 yrs... do you think CDI, unleaded, and better plugs these days reduce the risk of fouling much compared to the past? 

Edited March 14, 2019 by RedMesa

[Tom Droze]

Gosh guys, I’m feeling like such a pig; my trail tool bag weighs in at just under 3 kilograms or about 6.4 pounds, and that’s not including the rear rack it sits on. Then there is my spare inner tube, which sits atop my front fender (2.3 pounds). Then there is my Clarke fuel tank and that extra gallon of gas (6.3 pounds). But my shock, battery, and aluminum brake pedal did save me about 5.5 pounds. All in all, I suppose It’s a good thing I’m a full 50 pounds lighter than I was a year ago when I first bought my CRF — or did my weight loss upset the ratio of rider weight to bike weight? [emoji848]

[bajatrailrider]

You raise an important point. I go back and forth. Not currently carrying wrench and plug on CRF230F. Could be a big mistake and these items are not real large.
It does have an Iridium plug in it; bought that before I learned they are more for high compression engines.  Especially those run slower. For example, the Beta Xtrainer comes with Iridium while the race Betas don't, IIRC.
So, 50 yrs... do you think CDI, unleaded, and better plugs these days reduce the risk of fouling much compared to the past? 

No here is how I killed the plugs I said it only happened . 3 times ok now remember more then 3 times. Riding in Forest with cr500 . Slow hard trail it killed a plug first one in 12 years. TT 680 on death March trail Kennedy meadows . Xr600 many real deep water crossing. Caused bike to stall many kicks killed plug. My 230 twice old time cattle drive with cowboys. We where stuck behind them. At idle speed for long time. The 230 did not stop but running bad till I swapped plugs. Next plug on 230 the bike fell down. On it's side it took it's time to try to start. It would not start changed plug good to go. Non of this makes sense no matter. The new plug got me going again.

[RedMesa]

20 minutes ago, bajatrailrider said:

No here is how I killed the plugs I said it only happened . 

Thank you for the details. I'm going to start carrying again.

The Tusk holder is nice. I put some foam in to keep the plug from moving around. Be sure to check/set the plug gap.

https://www.rockymountainatvmc.com/parts/tusk-spark-plug-holder-p

[RedMesa]

12 hours ago, bajatrailrider said:

Seems like I need reduce spare parts in saddle bags. 

Just to give people ideas, here is my tool kit: http://bit.ly/2Fb94xM

[Chuck.]

1 hour ago, RedMesa said:

You raise an important point. I go back and forth. Not currently carrying wrench and plug on CRF230F. Could be a big mistake and these items are not real large.

It does have an Iridium plug in it; bought that before I learned they are more for high compression engines.  Especially those run slower. For example, the Beta Xtrainer comes with Iridium while the race Betas don't, IIRC.

So, 50 yrs... do you think CDI, unleaded, and better plugs these days reduce the risk of fouling much compared to the past? 

Iridium plugs are good, with regular plugs I change once a year. OEM plug on my X is a long life iridium, which is good because it is difficult to change.

I agree with packing all of that stuff because for long rides  I also pack a lot of stuff split between a fanny pack and a large fender pack.   However I have a lot of local knowledge of the area I usually ride and it has lots of logging roads so it is always easy to get back to staging.  I also wear SIDI Crossfires that are easier for walking than most other boots. As a result I leave my tools, except for screw drivers for mixture and clickers, in the truck. 
During one year I had two front flats on those trails but with a Tubliss I just finished the ride.

[RedMesa]

1 minute ago, Chuck. said:

I also wear SIDI Crossfires that are easier for walking than most other boots. 

Interesting. Only boots I have owned so I did not know how they compared. At one point I had to walk out and back several miles and they seemed to do well.

My KLX250s fell on a rock and broke a cooling line. Gorilla Tape worked for awhile but it all melted. Then I had to go to Walmart and get self-vulcanizing silicone tape. Long day.

This is why I like air-cooled bikes ?

[Chuck.]

21 minutes ago, RedMesa said:

Interesting. Only boots I have owned so I did not know how they compared. At one point I had to walk out and back several miles and they seemed to do well.

My KLX250s fell on a rock and broke a cooling line. Gorilla Tape worked for awhile but it all melted. Then I had to go to Walmart and get self-vulcanizing silicone tape. Long day.

This is why I like air-cooled bikes ?

Thanks. Since I have two water cooled bikes  I'll add a small roll to my chest pack.

Edited March 14, 2019 by Chuck.

[RedMesa]

6 minutes ago, Chuck. said:

Thanks. Since I have two water cooled bikes  I'll add a small roll to my chest pack.

Welcome. It's kind of amazing stuff. I left the repair on for a long time before finding a silicone hose kit and replacing them all.

[Chuck.]

I just remembered another trick to use for minor water leaks; turn the radiator cap to the vent position so there is no pressure in the radiator, that does lower the boiling point for the coolant but it will often slow a leak enough to allow limping out without losing all of the coolant.
The water pump is vulnerable so make sure you have enough protection. 

 

[RevyRoamer]

5 hours ago, mixxer said:

Another topic of weight is rotational mass....

Heavy wheels and tires, chains , sprockets being the core if this for me....

Not only do those parts have to be accelerated with the bike... They have to be accelerated in their own vectors/ rotations...

So they count for a lot more power absorption....

Pick a lighter rear tire ... You will think you just added compression when you next twist the throttle....

This is my thinking as well, yet it seems like half of the people add a very heavy tube as well. 

Heck i would like extra light tubes from stock, not heavy,  and would fill them with helium if i had it lol 

[bajatrailrider]

I just remembered another trick to use for minor water leaks; turn the radiator cap to the vent position so there is no pressure in the radiator, that does lower the boiling point for the coolant but it will often slow a leak enough to allow limping out without losing all of the coolant.
The water pump is vulnerable so make sure you have enough protection. 
 

I have another trick for Chuck. On water cooled bikes. Most have two water hoses I carry vise grip to block off one side if needed . Also a fitting so if I rip a hose make splice.

[bajatrailrider]

As far as 4mm heavy tubes. We only use those as not many flats. What is worse heavy tube or day with flat I'll light tube

[Chuck.]

Weight reduction is always a compromise to preserve functionality. I started a project to reduce the weight of a XR200R but got stuck at 208lbs, I have identified the path to less than 200lbs but I'm unwilling to give up functionality like traction, side stand, etc.
For some riding conditions a heavy flywheel is an advantage.
Weight up high is more noticeable so I always focus on those item like handlebars and tend to ignore weight that is closer to the CG of the bike.
Function is always important so I still have side stands on my bikes.
Aluminum rear sprockets are a big weight saver and they are unsprung and rotating. 
I use radial ply Competition Trials tires on the rear and although heavier than a knobby they provide more traction.

I have a modern Trials bike that weighs 165lbs ( a little heavy for a 250 Trials bike) and it has most of the same stuff as an offroad bike but every thing is scaled down. e.g. small brake rotors, small rear sprocket, only 1 radiator, no seat, small tank, aluminum axles, etc. Wonderful for tight technical gnarl but not for trail riding. I put a seat and larger tank on it for trail riding like some the Trials bikes mfg that call that market them as Long Rides;  I think a more descriptive name would be "Short Ride", which is the nickname I gave my Trials bike.

Edited March 14, 2019 by Chuck.